When you're looking to fill up your car with gas, how much thought do you really put into the process? Do you simply pull into the nearest gas station, or do you shop around a little, looking for the cheapest gas available? If you have your car's engine in mind, do you think about which type of gas will work best in your vehicle? In fact, a consumer and retail market research company, NPD Group, has identified two camps of gasoline seekers: those who look for the lowest prices out there and those who want better performance from their fuel [source: Greenberg].

All gas stations have to distribute gasoline that includes additives designed to clean important engine parts -- the Environmental Protection Agency (EPA) requires it. But if you've watched television or driven by a Shell gas station recently, you may have noticed advertisements for a special kind of gasoline with a fancy, vaguely scientific name: Shell Nitrogen Enriched Gasoline. In March 2009, the Shell gas company began pumping this gasoline at their stations, and they emphasized the fuel's formidable cleaning power.

­As fuel prices continue to jump around only to settle back down unexpectedly, many drivers are looking for more efficient ways to use and conserve fuel. There are several driving habits people can alter or improve, including paying attention to local speed limits and avoiding hard braking and rapid acceleration. But taking care of your car's engine is important, too. The performance of your vehicle's engine is a big factor in fuel economy. A properly maintained, well-cared-for engine will give you better fuel efficiency, and therefore you'll spend less time watching the prices tick away at the pump. The types of gas you use can affect your engine, too, and Shell would like you to think that its particular blend of gasoline will affect your engine positively.

So, how does Shell's nitrogen-enriched gas work in a car's engine? Does Shell's gas really perform better than other types of gasoline, or are they simply jumping onto the efficiency bandwagon with a gimmicky advertising campaign? Keep reading to find out.

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